Glycosphingolipids - antisera have been prepared to ganglioside GMl and asialo-GMl, and IgG and IgM fractions were prepared from these antisera by gel filtration chomatography on Sephadex G-200 columns. The IgG fraction from anti-asialo-GMl sera reacted very specifically with the immunizing antigen by complement fixation assay, and exhibited little cross-reactivity with other glycolipids. In contrast, the IgG fraction of anti-GMl sera exhibited extensive cross-reactivity with asialo-GMl and ganglioside Gdlb. Nuclear Magnetic Resonance Studies - Binding of alpha- and beta-Methyl-D-glucopyranosides (uniformly labeled with 14 percent C13) to concanavalin A was studied by pulsed Fourier transform carbon magnetic resonance techniques. The spin-lattice relaxation times (Tl) for the carbon resonances of the two glycosides were measured in the presence and absence of the zinc and manganese derivatives of the protein. Tl values for the ring carbons of both sugars were uniformly shortened when bound to zinc Con A and selectively shortened when bound to manganese Con A. These results indicate that the paramagnetic manganese ion in Con A contributes to the relaxation of the carbon atoms of bound sugars. These measurements permitted calculation of the distance between each carbon atom of the bound sugars and the manganese ion, and made it possible to calculate the 3-dimensional orientation of both sugars relative to the transition metal site in the protein.